To determine appropriate ratio for intercropping of oat and berseem clover under manure application levels, a field experiment was carried out as split-plot arrangements using randomized complete block with three replications in 2015-2016 cropping season at Ramin Agricultural and Natural Resources University of Khuzestan, Ahvaz, Iran. Experimental treetments included: manure: 0, 12, 24, 36 ton.ha^-1 from composted cow manure were assigned to main plots, and five ratio of oat mixed cropped with breseem clover: I: sole crop of oat, II: 75% oat+ 25% clover, III: 50% oat+ 50% clover, IV: 25% oat+ 75% clover, V: clover sole cropped were randomized in sub-plots. Results showed that the highest dry forage yield (12849 kg.ha^-1) and crude protein yield (2404 kg.ha^-1) obtained from 50 % oat+ 50 % clover and application of 36 ton.ha^-1 of manure. The highest forage crude protein conten (%) and dry matter digestibility obtained from sole cropping of berseem clover and application of 36 ton.ha^-1 of manure. The highest forage ash observed in 75% clover+ 25% oat and highest water soluble carbohydrate, NDF and ADF measured in sole cropping of oat. 50% oat+ 50% berseem clover with application of 36 ton.ha^-1 of manure had the highest LER (1.53) as compared with other mixed cropping ratios.